Tortoise Merge 1.9.3, the difference viewer that comes with the Tortoise Subversion client, has in its settings dialogue a tick-box setting for “Enable Editor Config”, just right of the “Tab Size” setting. The help for this dialogue does not describe this option, nor could I find it on-line, and I did not observe any effect of setting it — what does it do?
editorconfig is a format to specify how an editor should treat tab/spaces and other settings. Since TortoiseMerge can also edit files, it can use the config files in editorconfig format and act accordingly.